Organic polymers (plastics) and in particular polyolefins, such as polyethylene and polypropylene require, the addition of various additive systems thereto in order both to be processed and to retain long term stability in order to retain desired service properties. In addition to the damaging influence of light and heat, residues of the catalyst system used in the production of such plastics are also detrimental. To overcome such difficulties, a wide variety of substances are known in the art for use as additives and stabilizers. In many instances a mixture of such additives is employed.
One commonly used additive system is that comprising a sterically Nov. 17, 1998 hindered phenol antioxidant which is employed in combination with an acid neutralizer. Since such antioxidants and acid neutralizers are in the powder form, there is presented a disadvantage in the use of same in an additive system due to the problem of dusting as well as having a tendency toward separation and proving difficult to meter. Thus there exists a need for a commercial form of antioxidant additives which does not have these disadvantages.
While a variety of approaches have been made to achieve the production of a low dust additive system, such processes have generally employed systems that introduce into the additive package a further component such as calcium stearate, water, or other binders.
Other prior art systems using mixing processes or compacting are known, but in most cases the resulting commercial forms do not have adequate mechanical properties.
In addition to an additive package having adequate mechanical strength or hardness so as to have sufficient abrasion resistance to preclude dust formation, such an additive package also needs to have a balanced hardness which will permit it to be readily processed in the systems wherein the additive package is being dispersed into the host plastic.
Accordingly, there remains a need for a balanced strength antioxidant-acid neutralizer additive system which possesses adequate mechanical strength to avoid mechanical abrasion and dust formation while at the same time having a balanced hardness which will permit it to be readily dispersed in the host plastic, while at the same time avoiding the introduction of undesired components.
Since the agglomerated additive systems of the present invention have a spherical shaped structure, such agglomerates exhibit good flow characteristics which permit the use of softer particles to achieve good metering and better dispersability of the additive system into the host plastic.
In addition, by controlling the hardness of the agglomerated additive package in accordance with the present invention, there is provided a process for the production of customized agglomerate additive systems.
It is thus an object of the present invention to provide a process for the production of novel aggregate of a sterically hindered phenol antioxidant and an acid neutralizer blends which will avoid the introduction of undesired components into the additive system.
Another object of this invention, is to provide a novel sterically hindered phenol-acid neutralizer additive system in an agglomerated form which will have a balanced hardness so as to provide adequate abrasion resistance yet being readily dispersed in a host plastic.
Other aspects, objects, and the several advantages of this invention will become apparent from the following specification and claims.